Currently WLANs are finding more and more extensive use in the field of information science and videographic communication for the purpose of transmission and distribution of data and other information among multiple users located inside the same building (for example, among personal computers, laptop computers, printers and other users without any restrictions on the “mobility” of these devices). Transmission of information with the use of WLAN allows one to reduce network cost because there is no necessity of laying connecting wires. A network of this type can be also used in those cases when it is either difficult or impossible to lay connecting wires and in cases when there are no socket connectors for local networks due to architectural restrictions. WLAN represents an ideal solution for an institution at which the arrangement of users is often changed. In existing WLANs, radio communication is usually arranged in compliance with known international standards, such as IEEE 802.11, IEEE 802.11a, IEEE 802.11b, ISO 8802-11 and HIPELAN of type 2. Temporary networks (i.e. the networks in which number of users may vary and information can be transmitted under the control of network coordinator either simultaneously to an arbitrary number of users or directly from one user to another) are arranged based on the above-mentioned standards.
The known methods for radio communication in a WLAN are based on the use of both permanent and temporary coordinators of a network—that is, devices that provide for the conditions for the exchange of information between any users belonging to a given network (See U.S. Pat. Nos. 5,912,921; 6,026,303 and 6,075,780; U.S. patent application Ser. Nos. 09/797,085; 09/773,418; 09/795,003; and 09/736,600; Great Britain No. 9900593; and EPO Application Serial No. 0859490). These methods and adequate equipment allow one to arrange the ad-hoc networks intended for the simultaneous transmission of information to an arbitrary number of users (including mobile users).
For instance, the method of operation of a wireless radio communication system that includes a controller and a plurality of stations, each of which is equipped with a transmitting and receiving device is known (See U.S. patent application Ser. No. 09/773,418). The transmission of information from one station to another in the known method is performed at time slots assigned for each station by the controller. In this process a receiving station hstores information related to parameters of transmission by all other stations, and prior to the reception of a signal from a transmitting station said receiving station tunes its receiving device in accordance with the stored parameters of transmission of transmitting station—for example, signal level or frequency offset.
This method makes it possible to make the requirements to receiving devices of system stations less stringent. At the same time the use of the omnidirectional radiation of signal in this method limits the range radio communication system determined predominantly by the radiating power of a transmitting device and sensitivity of a receiving device, which parameters usually can not be enhanced significantly for WLAN users. Besides, the known method doesn't ensure sufficient reliability of radio communication due to possible influence of multipath interference in a signal reception point and due to the signal fading effect.
The known method is used in a radio communication system (See U.S. patent application Ser. No. 09/773,418) including a controller and a plurality of stations, and transmission of data in such a system is carried out at time intervals (time slots) allocated for each station by the controller. Each station in such a system is equipped with a transmitting and receiving devices plus a means intended for storing information on parameters of transmission by all other stations of the system and a means for tuning station's receiving device prior to receiving signal from transmitting station, with said tuning being dependent on stored information about the parameters of a signal from the transmitting station.
The known wireless communication system makes it possible to make the requirements to receiving devices of system stations less stringent. However, the use of omnidirectional antennas in transmitting and receiving devices of stations of this system has an adverse effect on the range of system stations. Besides, sufficient reliability of radio communication in the known wireless communication system is not ensured due to possible influence of multipath interference in a signal reception point and due to the signal fading effect.
Another method of the operation of an ad-hoc wireless network including a plurality of stations, each of which is equipped with a transceiver connected to antenna device for the purpose of communication with other stations of the network, is known (See U.S. patent application Ser. No. 09/797,085). Each station of the network is capable of operating both as a “master” station (i.e. coordinator) and as a “slave” station. Besides, each station is capable of determining rank for every other station with said rank being representative of other station suitability for performing the role of master station in a network. According to this method, at least one of the stations is capable of determining the rank of all stations in the network for performing the role of a “master” station (i.e. coordinator), and the station having the highest rank is selected as a “master” station (i.e. coordinator).
The known method allows nominating such a station as a network coordinator that is characterized by the best potential for the performance of this function. However, it is not possible to change the network coordinator in the known method when the conditions of network functioning are changed. Besides, the employment of the omnidirectional radiation of signal in the known method limits the range of stations in the network.
The known method is practically implemented in a wireless network (See U.S. patent application Ser. No. 09/797,085) that includes a plurality of stations. Each station in the network is equipped with a transceiver connected to an antenna device, a controller for the purpose of performing the role of a “master” or “slave” station and a device for determining a rank for the station suitability for performing the role of the master station in the network. At least one of the stations is equipped with a special means for determining the rank of all stations in the network and means for delegating the role of a “master” station (i.e. coordinator) to a station having the highest rank.
The known wireless network performs the appointment of such a station as a network coordinator that is characterized by the best potential for the performance of this function. However, this network is incapable of changing the network coordinator (“master” station) in the network. Besides, the employment of omnidirectional antennas in this system limits the range of stations.
In terms of the entire set of essential features, the closest method to the invention claimed herein is the method for radio communication in an ad-hoc WLAN consisting of a plurality of transceivers, that implies selection of at least one transceiver as a temporary coordinator of said network, switching-over other transceivers into the client state, and collection by said temporary coordinator from each transceiver of data on their location and communication conditions with each client transceivers (See U.S. Pat. No. 6,026,303). If said temporary coordinator is incapable of collecting said data from all transceivers it switches-over to the state of a client transceiver, while one of the other transceivers is selected as a temporary coordinator of the network based on data on location of client transceivers in the network and conditions of communication with each client transceivers. The procedure described above is repeated until such a temporary coordinator is found that would be capable of collecting data on location of all client transceivers in the network and conditions of communication with each client transceivers. Such a temporary coordinator is then becomes a permanent coordinator of the network.
The known prototype method (See U.S. Pat. No. 6,026,303) allows one to choose such a transceiver as a coordinator that is capable of communicating with all transceivers of the network. However, the use of omnidirectional radiation of signal by client transceivers in this method limits the range of these transceivers in the network.
The prototype method is practically implemented through the use of an ad-hoc WLAN consisting of a plurality of transceivers, each of which includes a setting unit intended for setting a transceiver into the mode of temporary or permanent coordinator of the WLAN (when a signal for setting in these states is received) and for setting it into the client mode (when said signal is not received), a data collection unit intended for collecting data from each client transceiver about its location and conditions of communication with each client transceiver when the transceiver is switched-over into the temporary coordinator mode and a coordinator selection unit intended for selecting temporary coordinator, permanent coordinator and for transmitting a signal for setting into the state of temporary or permanent coordinator of the WLAN (See U.S. Pat. No. 6,026,303).
The known prototype ad-hoc WLAN allows one to choose such a transceiver as a coordinator that is capable of communicating with all transceivers of the network. However, the use of omnidirectional radiation of signal by client transceivers limits the range of these transceivers in the network.